Sound-directing appliance.



E. M. C. TIGERSTEDT; SOUND DIRECTING APPLIANCE. APPLICATION FILEDMAYI'Z, 1915.

Patented Aug. 20, 19181 said nineties oaMrBEILL rxenns'runr, oroornnnnonn, ENMARK.

. soUnD-nnanofrme nrrmanoii.

To all whom it may! concern: I Be it known that I, Emo- MAGNUS CAMP-BELL TIeERsrED'r, a subject of the Emperor of Russia, residing atCopenhagen, "Denmark, have invented certain new and useful Improvementsin Sound-Directing Appli-.

ances 'pf. which the following is a specification. i

This invention relates to diaphragms and particularly to such as areused for ,gramophones, phonographs, talklng or recordingmachines,-receivers or transmitters of telephone's, or other similardevices in whichdiaphragms are employed for receiving, recording orproduclng sound waves,

In" devices of the type referred to it was common'practice to provide,opposite the diaphragm, a guide for the sound waves, as, for instance, amouth-piece or thelike,-having'aoentra-lopening for the passage of thesound waves. Since-the central opening in theguide' was usuallycomparatively small the massof the diaphragm caused to vibrate bythesound waves was also comparatively small. Thus, with devices, asheretofore constructed, much difliculty' has been exper encedjintransmitting'sound waves to somewhat far distances, and .no "mechanismhas,

to myknowledge, heretoforebeen' devised embodying any practicable meansfor enablingija clean transmission of sound waves to'fa'r distances sothat they will be clearly comprehended at distant places.

The object of the present lnvention is to obviate the aforesaiddifi'iculties and to correct a vital imperfection. .To this end-'1provide means whereby the sound waves will be conveyed from the rim ofthe diaphragm to its center and vice versa, thereby enabling.

the diaphragm topbe acted upon by or to produce a greater quantity ofsound waves.

In the drawings several constructional forms of the arrangementaccording to the invention are shown.

tion, of a diaphragm for producing sound waves by means of a recordplate.

Fig. 2 is a similarv sectional view showing a receiver provided with theinvention.

Figs.';3 and 4 are similar-sectional views showing ,two otherembodimentsof the invention;

' Referring to Fig. 1, dis a diaphragm from the rim fjof which extends adiverging funnel or trumpet a. In the funnel or trumpet a a-certaindistance apart from and opposite Specification of Letters "Patent Figure1 is a side elevation, partly in sec-v v Patented Aug. so, rare.

' Application filed'May 12,11915. Serial No. 27,580.

the diaphragm d is fixed by means of bands or straps 0 a wall,preferably of special shap'eas will be afterward explained-or a cone 7),The wall or the base of the cone 2) is so arranged in the trumpet'a asto leave an annular gap for the passage of the sound waves between itscircumference. and the smaller end of the trumpet a.

In the constructional form, as shown in F g.1, the diaphragm d isvibrated or operated upon by means. of a bell-crank levere I pivoted atf and provided with a stylus which is actuated by the records on therecord plate hi and cone 3) is similar tothat in-Fig. 1. In the base ofthe hollow cone 6 a magnet g is provided the coils of which are wound inanopposite direction to the windings of a mag net .11 arranged below thediaphragm d. The windings of the two magnets are connected in series ina telephonev exchange, not shown.

Normally the forces of the two magnets neutralize each other, and,therefore, the diaphragm will remain perfectly plane. in operation themagnetic force of the one electro-magnet will be increased, and that ofthe other decreased. This arrangement results in perferctly equalover-vibrations of'the diaphragm whichare independent of the position ofthe'latter; The amplitude of the diaphragm also becomes larger and morevigorous. 4

The efliciency may generally be still further increased by providing thebase of the-cone lgj-in the form of another diaphragm, as shown in Figs.3 and 4.

Fig. 3 illustrates the invention as applied to a transmitter. {Thediaphragm d is provided at the smaller end of a mouth-piece a" andcooperates with a carbon grain microphone la. -This carbon grainmicrophone k is connected .in series carbon grain microphone Z providedin the with another hollow-cone b the-base of which forms a sec- 0nddiaphragm n opposite the first dia- "phragm 03. The sound waves enteringthe mouth-piece a. pass through the annular gap 0 and 'move in a radialdirection to the center ofthe diaphragms d and n. At the center. theywill hit upon each other and cause an energetic vibration of the dia-'phragms. v The receiver according to Fig. 4 differs In Fig. 2 theinvention is shown in connection with a receiver. The general ar- 9rangement of the diaphragm d, trumpet w from the construction shown inFig. 2 in that the base 01 the cone 5 provides a second diaphragm popposite the diaphragm (Z. and that the electro-magnet 9 does notproject through the. base'ot but is inclosed in the cone Z2.

1. In a sound directing appliance, the combination of a diaphragm, afunnel, the opening of which is in direct opposition to the diaphragm,and means including a portion provided with a plane surface closelyoverlying the diaphragm for conveying the sound waves from the rim ofsaid diaphragm to the central portion of the same, and vice versa.

2. In a sound directing appliance, the

' combination of a diaphragm, a funnel, a

conesshaped element within said funnel, the base wallof said cone beingin direct and close opposition to the diaphragm, the base portion of thecone being located centrally within the narrower opening of the funnel,

whereby an annular gap is formed-between the rim of said opening and thebase of the cone, for directing the sound waves from said annular gapnear the circumference of the diaphragm toward the central portion v ofthe same, and vice versa.

3. In a sound directing appliance, the combination of a diaphragm, afunnel, a closed cone-shaped element within said tunnel, the closingbase of said cone being in direct and close opposition to the diaphragm,the base portion of the cone being located centrally within the narroweropening of the funnel, whereby an annular gap is formed between the rimof said opening and the base of the cone, for directing the sound Wavesfrom said annular gap near the circumference'of the diaphragm toward thecentral'portion of the same, and vice versa;

and means for'imparting vibrations to said diaphragm.

4:- In a sound directing appliance, the

ga arass? combination of a diaphragm, a funnel, a cone within saidfunnel, a second diaphragm forming the base wall of said cone and indirect opposition to the first named diaphragm, whereby an annular gapis formed between the narrower end of the funnel andthe base wall of thecone, for directing the sound waves from said annular gap at thecircumference of the first named diaphragm toward the central portion ofthe same, and vice versa,

5. In a .sound directing appliance, the combination of a diaphragm, afunneL-a cone in said funnel, a second diaphragm forming the baseportion of said cone and in direct opposition to the first nameddiaphragm, whereby an annular gap is formed between the narrower end ofthe funnel and the base portion of the cone, for directing the soundwaves from said annular gap'at the circui'nterence of saidfirst nameddia phragm toward the central portion of the same, and vice versa, andelectromagnets cooperating with both of said diaphragms.

6. In a sound directing appliance, the combination of a diaphragm, afunnel, a cone in said funnel, a second diaphragm forming the baseportion of the cone and in direct opposition to said first nameddiaphragm, whereby an annulargap is formed between the narrower end ofthe funnel and the base portion of the cone, for directing the soundwaves from said annular gap near the circumference of the first nameddiaphragm toward. the central portion of the same, and vice versa, andtele phone magnets for imparting vibratory mo tion to both of saiddiaphragms.

In testimony whereof I afliX my signature in presence of two witnesses.

ERIC MAGNUS CAMPBELL TIGERSTEDT.

lVitnesses: Vreoo BLOEoJ A. IV. AHLSTADT.

